The present invention relates to a printer, copier, facsimile apparatus or similar image forming apparatus including a paper feeding mechanism, and more particularly to a paper roll supporting device for supporting a paper roll applicable to the image forming apparatus.
It is a common practice with an image forming apparatus to set a paper roll by use of a spool type of member. This kind of scheme allows a paper roll to be supported over its entire width and allows a spool to be directly positioned by opposite side walls of the apparatus. The paper roll therefore shakes little and is easy to transport. However, in a large-scale machine capable of dealing with paper of up to size AO, the spool is as long as 1 m and makes the attachment and detachment of a paper roll difficult. For this reason, the spool scheme is not feasible for a large-scale machine.
On the other hand, Japanese Utility Model Laid-Open Publication No. 64-43048 and Japanese Utility Model Publication No. 7-48598 each propose to fit flanges in opposite ends of a paper roll and position the flanges on rollers. Specifically, Laid-Open Publication No. 64-43048 discloses a paper roll supporting device including a support wheel, a nut, and a screw. The support wheel includes a cylindrical portion whose outside diameter is slightly smaller than the inside diameter of an axial center bore formed in a paper roll. A plurality of axial slits are formed in the circumferential wall of the cylindrical portion. A flared flange extends out from one end of the cylindrical portion. The nut has a conical pressing surface contacting the inner periphery of the open end of the cylindrical portion. The screw connects the nut to the support wheel. The screw presses the inner wall of the tubular core of the paper roll via the flange, exerting a great retaining force. This kind of device, however, forces the operator to drive the screw and perform other troublesome operations at the time of setting.
On the other hand, Publication No. 7-48598 teaches a paper roller supporting device including a body member to be inserted into the core of a paper roll an end support member that supports the paper roll. An auxiliary member is inserted in a through hole formed in the body member. A plurality of arm members protrude from the body member in the direction in which the end support member is to be inserted into the core. A lug protrudes from each arm member toward the wall of the through hole. The auxiliary member includes a tubular portion to be received in the through hole of the body member. Lug members protrude from the outer circumference of the tubular member, and each is formed with a recess at its top. When the auxiliary member is inserted into the body member and rotated bout is own axis, the lugs of the arm members mate with the recesses of the lug members while the arm members flare and press the inner periphery of the core. This kind of configuration effectively presses the inner periphery of the core by using an elastic force available with resin. However, because the cylindrical member is rotated to elastically deform the resin members with the lugs, the body member itself rotates together with the cylindrical member unless the operator holds the flange.
It is therefore an object of the present invention to provide a paper roll supporting device for an image forming apparatus including improved flanges for promoting easy setting operation.
A paper roll supporting device for an image forming apparatus of the present invention includes a pair of flange members to be inserted into opposite ends of a paper roll. Each flange member includes a flange body made up of a flange portion and a cylindrical support portion that is to be inserted into a tubular core included in the paper roll. A claw member has a plurality of claws capable of protruding from the outer circumference of the support portion. A biasing member exerts a pressure on the claw member. Pressing means is slidable in a direction in which the biasing member is compressible. The pressing means receives one end of the biasing member and contacts the inner circumference of the support portion. A lock/release lever is capable of being brought down for causing the pressing means to slide. The claw member causes its pawls to flare in the radial direction when pressed in the axial direction of the support portion.